A Unique CaMKIIβ Signaling Pathway at the Centrosome Regulates Dendrite Patterning in the Brain

The protein kinase calcium/calmodulin-dependent kinase II (CaMKII) predominantly consists of the α and β isoforms in the brain. Although CaMKIIα functions have been elucidated, the unique catalytic functions of CaMKIIβ have remained unknown. Using knockdown analyses in primary neurons and in the rat cerebellar cortex in vivo, we report that CaMKIIβ operates at the centrosome in a CaMKIIα-independent manner to drive dendrite retraction and pruning. We also find that the targeting protein PCM1 localizes CaMKIIβ at the centrosome. Finally, we uncover the E3 ubiquitin ligase Cdc20-APC as a novel centrosomal substrate of CaMKIIβ. CaMKIIβ phosphorylates Cdc20 at Ser51, which induces Cdc20 dispersion from the centrosome, thereby inhibiting centrosomal Cdc20-APC activity and triggering the transition from growth to retraction of dendrites. Our findings define a novel isoform-specific function for CaMKIIβ that regulates ubiquitin signaling at the centrosome and thereby orchestrates dendrite patterning, with important implications for neuronal connectivity in the brain.